Method of singulating semiconductor die and method of fabricating semiconductor package

light source: LD excitation Q-switch Nd:YVO4 laser

wavelength: 1064-nm pulsed laser

pulse output: 10 microjoules

diameter of converging spot: 1 micrometer

repetition frequency: 100 kHz

moving speed: 100 mm/s

light source: LD excitation Q-switch Nd:YAG laser

wavelength: 1064-nm pulsed laser

pulse output: 20 microjoules

diameter of converging spot: 1 micrometer

repetition frequency: 100 kHz

moving speed: 100 mm/s.

FIG. 3 is a cross-sectional view of a stage on which an adhesive film 20 A and a base film 30 A are sequentially added to the semiconductor substrate 10 in which the modified layer 10 m has been formed.

Referring to FIG. 3 , the adhesive film 20 A is referred to as a die attach film (DAF) and may be attached to the second surface 10 b of the semiconductor substrate 10 .

The base film 30 A may be attached to the adhesive film 20 A. The base film 30 A may include a polymer of polyolefin series such as polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polypropylene (PP). In particular, the base film 30 A may have elasticity such that the base film 30 A may be expandable in a lateral direction, i.e., a direction parallel to a top surface of the base film 30 A.

The base film 30 A may include an adhesive releasing layer 32 at a surface contacting the adhesive film 20 A. For example, the base film 30 A may contact the adhesive film 20 A through the adhesive releasing layer 32 . The adhesive releasing layer 32 may bond the base film 30 A to the adhesive film 20 A and allow the base film 30 A to be easily detached from the adhesive film 20 A by ultraviolet (UV) exposure. The adhesive releasing layer 32 may include a photoinitiator which is activated by UV exposure and initiates a reaction decreasing adhesion.

The adhesive film 20 A and the base film 30 A may be commercial films.

While the partition lane 10 L is expanded in a left-and-right direction in FIG. 2B , the partition lane 10 L is expanded in the direction of a line of sight in FIG. 3 . However, since the partition lanes 10 L extend crossing one another in a lattice pattern as shown in FIG. 1 , partition lanes 10 L that are expanded in the left-and-right direction exist in the semiconductor substrate 10 in the line of sight in FIG. 3 although not directly shown.

FIG. 4 is a lateral cross-sectional view of a stage on which semiconductor dies 10 S are singulated by expanding the base film 30 A in the lateral direction, i.e., the direction parallel to the top surface of the base film 30 A.

Referring to FIG. 4 , when the base film 30 A is expanded, lateral stress may be applied to the semiconductor substrate 10 . A crack formed in the modified layer 10 m may propagate in the thickness direction (i.e., a direction perpendicular to the top surface of the base film 30 A) of the semiconductor substrate 10 due to the lateral stress. The crack has been described above with reference to FIGS. 2A and 2B . Thus, the semiconductor dies may be separated from each other by applying a force (e.g., lateral stress) to the semiconductor substrate 10 in a lateral direction.

Expansion of the base film 30 A may be performed at a temperature lower than room temperature. In an exemplary embodiment, the base film 30 A may be expanded at a relatively lower temperature of about −20° C. to about 10° C., about −15° C. to about 5° C., about −15° C. to about 0° C., or about −15° C. to about −10° C. The expansion of the base film 30 A is performed at the relatively lower temperature because disruption of the adhesive film 20 A may be increased if the expansion of the base film 30 A is performed at a temperature higher than 10° C.

The base film 30 A may be expanded by a length of about 1 mm to about 9 mm, about 1.5 mm to about 7 mm, about 2 mm to about 6 mm, or about 3 mm to about 5 mm, but the inventive concept is not limited thereto.

A distance “d” in a direction parallel to the top surface of the base film 30 A between adjacent semiconductor dies 10 S may be substantially regular. The distance “d” may vary with the amount of lateral expansion of the base film 30 A. The distance “d” may be greater than the width of the partition lanes 10 L.

In an exemplary embodiment, the distance “d” may be about 10 μm to about 100 μm, about 30 μm to about 80 μm, or about 50 μm to about 70 μm, but the inventive concept is not limited thereto.

To apply lateral stress to the semiconductor substrate 10 , the base film 30 A may be expanded in the lateral direction using various methods. For example, in some embodiments, the semiconductor substrate 10 may be lifted upward in a state where the edge of the base film 30 A is fixed. In this exemplary embodiment, the base film 30 A may be expanded in the lateral direction in proportional to the amount of lift of the semiconductor substrate 10 , and therefore, lateral stress may be applied to the semiconductor substrate 10 .

FIG. 5 is a lateral view of a stage on which warpage occurs in semiconductor dies 10 W, which have been singulated, and an adhesive film 20 B.

Referring to FIG. 5 , warpage may spontaneously occur in the semiconductor dies 10 W due to various causes. In an exemplary embodiment, the warpage may occur because the influence of stress caused by metal wires in active surfaces (i.e., top surfaces in FIG. 5 ) of the semiconductor dies 10 W increases as the semiconductor dies 10 W become very thin.

In another exemplary embodiment, the warpage may occur because the adhesive film 20 A is not expanded while the base film 30 A is expanded in the lateral direction. For example, the base film 30 A and the adhesive film 20 A may be flatly bonded to each other before the base film 30 A is expanded. However, when the base film 30 A is expanded in a horizontal direction, with the size of the adhesive film 20 A being constant, stress occurs in the bonding interface between the base film 30 A and the adhesive film 20 A, and therefore, warpage may occur.

FIG. 6 is a lateral view of a stage on which a protective film 40 is provided above the semiconductor dies 10 W and the adhesive film 20 B in which warpage occurs.

Referring to FIG. 6 , the protective film 40 may be provided to cover the semiconductor dies 10 W and the adhesive film 20 B, which have the warpage.

The protective film 40 may not be rigid but may have flexibility. The protective film 40 may readily transmit pressure from above to below. The protective film 40 may include polymer resin such as PE, PP, PET, or polystyrene.

A gas injection system 50 which sprays gas onto the protective film 40 may be provided above the protective film 40 . Gas may be supplied to the gas injection system 50 . The gas may be discharged toward the protective film 40 through nozzles 54 formed in a body 52 of the gas injection system 50 .

The discharged gas may apply pressure to the protective film 40 . Since the protective film 40 has flexibility, the protective film 40 may readily transmit the pressure to the semiconductor dies 10 W and the adhesive film 20 B, which are located below the protective film 40 . In particular, when a film having relatively high flexibility is selected as the protective film 40 (e.g. a film that is bendable and not rigid), when the discharged gas applies pressure to the protective film 40 , the protective film 40 may come in close contact with the surfaces of the semiconductor dies 10 W, and therefore, the pressure may be more effectively transmitted. For example, when a film having relatively high flexibility is selected as the protective film 40 and when the discharged gas applies pressure to the protective film 40 , the protective film 40 may contact a relatively higher percentage of the surfaces of the semiconductor dies 10 W compared to when a film having relatively low flexibility is selected as the protective film 40 . For example, when a film having relatively high flexibility is selected as the protective film 40 , the protective film 40 may contact about 75% or more of the surfaces of the semiconductor dies 10 W when pressure is applied to the protected film 40 by the gas discharged from the gas nozzles 54 and when a film having relatively low flexibility (e.g., relatively rigid) is selected as the protective film 40 , the protective film 40 may contact about 50% or less of the surfaces of the semiconductor dies 10 W when pressure is applied to the protected film 40 by the gas discharged from the gas nozzles 54 .

The gas that is sprayed may be air or a gas, such as nitrogen (N 2 ), carbon dioxide (CO 2 ), helium (He), neon (Ne), or argon (Ar), which is chemically low-active or inert.

Although the protective film 40 covers the semiconductor dies 10 W in FIG. 6 , the protective film 40 may be omitted in some example embodiments. When the protective film 40 is omitted, gas sprayed by the gas injection system 50 may directly apply pressure to the top surfaces of the semiconductor dies 10 W.

When the protective film 40 is used as shown in FIG. 6 , the distribution of pressure applied to the semiconductor dies 10 W may be more uniform and the warpage of the semiconductor dies 10 W and the adhesive film 20 B may be reduced or alleviated by the gas sprayed from the gas injection system 50 . When the protective film 40 is omitted differently from FIG. 6 , the semiconductor dies 10 W positioned respectively corresponding to the nozzles 54 may receive higher pressure and the warpage of the semiconductor dies 10 F and the adhesive film 20 B may be reduced or alleviated by the gas sprayed from the gas injection system 50 . However, when the protective film 40 is omitted differently from FIG. 6 , the percentage of warpage reduction of the semiconductor dies 10 F and the adhesive film 20 B may be less than the percentage of warpage reduction of the semiconductor dies 10 F and the adhesive film 20 B when the protective film 40 is used as shown in FIG. 6 .

FIG. 7 is a lateral view of a stage after warpage of semiconductor dies 10 F and the adhesive film 20 B is alleviated.

Referring to FIG. 7 , the warpage of the semiconductor dies 10 F and the adhesive film 20 B may be reduced or alleviated by the gas sprayed from the gas injection system 50 . Accordingly, detachment of the semiconductor dies 10 F and the adhesive film 20 B from the base film 30 A may be reduced or prevented.

In some exemplary embodiments, the semiconductor dies 10 F and the adhesive film 20 B may become in close contact with the base film 30 A due to the gas sprayed from the gas injection system 50 .

FIG. 8 is a lateral view of a stage on which the adhesion between the adhesive film 20 B and the base film 30 A is reduced or removed by irradiating UV rays to the base film 30 A.

Referring to FIG. 8 , UV rays may be irradiated at the base film 30 A to separate the semiconductor dies 10 F from the base film 30 A. The adhesion between the adhesive film 20 B and the base film 30 A is removed or reduced by the UV rays, and thus, the semiconductor dies 10 F may be separated from the base film 30 A. In an exemplary embodiment, as described above with reference to FIG. 3 , a photoinitiator included in the adhesive releasing layer 32 may be activated by the UV rays and initiate a reaction decreasing the adhesion between the adhesive film 20 B and the base film 30 A.

The activation of the photoinitiator may be hindered in an atmosphere including oxygen. For example, even though UV rays are radiated, the reaction initiated by the photoinitiator of the adhesive releasing layer 32 may be hindered in an atmosphere, such as air (e.g., atmospheric air), including oxygen, and therefore, the adhesion between the adhesive film 20 B and the base film 30 A may be maintained instead of being reduced. Accordingly, due to oxygen present at the partition lanes, when UV rays are radiated in a state where the edge of the adhesive film 20 B is detached from the base film 30 A (e.g., partially detached state of the semiconductor dies 10 F), adhesion is maintained at the portion adjacent to the detached portion. The semiconductor dies 10 W and the adhesive film 20 B, which have had warpage, may be relieved from the warpage several minutes to several tens of minutes later and may be in full physical contact with the base film 30 A. In this case, the adhesive film 20 B is still chemically attached to the base film 30 A at the portion where the adhesion has been maintained, i.e., the portion just adjacent to where the detachment has occurred due to the warpage. As a result, when the semiconductor dies 10 F are picked up in expectation of being easily separated due to the UV radiation, the semiconductor dies 10 F may not be picked up or may be damaged because of the re-attached portion.

Therefore, in some embodiments, only when the adhesive film 20 B is in full contact with the base film 30 A, as shown in FIG. 8 , before UV radiation, the photoinitiator of the adhesive releasing layer 32 may be normally activated. For example, only when the entire bottom surface of the adhesive film 20 B is in contact with the top surface of the adhesive releasing layer 32 and the entire bottom surface of the adhesive releasing layer 32 is in contact with the top surface of the base film 30 A, as shown in FIG. 8 , before UV radiation, the photoinitiator of the adhesive releasing layer 32 may be normally activated. In addition, since adhesion is reduced throughout the whole area of the adhesive film 20 B contacting the base film 30 A because of UV radiation, the semiconductor dies 10 F may normally and smoothly be picked up in a pick-up process afterward.

FIG. 9 is a lateral view illustrating a semiconductor die 10 F that is being picked up and detached from the base film 30 A on a stage.

Referring to FIG. 9 , while the semiconductor die 10 F to be picked up is being supported by a needle 64 , a collet 62 may vacuum-adsorb and lift up the semiconductor die 10 F to detach the semiconductor die 10 F from the base film 30 A and may move the semiconductor die 10 F to a desired position.

FIGS. 10A and 10B are lateral views for explaining a method of singulating the semiconductor dies 10 W, according to an exemplary embodiment of the inventive concept.

The embodiment illustrated in FIG. 10A is substantially the same as that illustrated in FIG. 6 with the exception of spraying gas from below the base film 30 A. Thus, redundant descriptions will be omitted, and differences will be described below.

A first gas may be sprayed toward the tops of the semiconductor dies 10 W by a first gas injection system 50 A provided above the protective film 40 . A first pressure P 1 may be applied to the tops of the semiconductor dies 10 W by the spraying of the first gas. The first gas may be sprayed toward the tops of the semiconductor dies 10 W through nozzles 54 A formed in a body 52 A.

A second gas may be sprayed toward the bottoms of the semiconductor dies 10 W in a direction opposite to the sprayed direction of the first gas by a second gas injection system 50 B provided below the base film 30 A. A second pressure P 2 may be applied to the bottoms of the semiconductor dies 10 W by the spraying of the second gas. The second gas may be sprayed toward the bottoms of the semiconductor dies 10 W through nozzles 54 B formed in a body 52 B. The first pressure P 1 may be equal to or greater than the second pressure P 2 .

Referring to FIG. 10B , the warpage of the semiconductor dies 10 F and the adhesive film 20 B may be reduced or alleviated by the first gas and the second gas respectively sprayed from the first and second gas injection systems 50 A and 50 B. Accordingly, detachment of the semiconductor dies 10 F and the adhesive film 20 B from the base film 30 A may be reduced or prevented.

In some exemplary embodiments, the semiconductor dies 10 F and the adhesive film 20 B may become in close contact with the base film 30 A due to the first and second gases respectively sprayed from the first and second gas injection systems 50 A and 50 B.

Subsequent processes are the same as those described with reference to FIGS. 8 and 9 . Thus, redundant descriptions will be omitted.

FIGS. 11A and 11B are lateral views for explaining a method of singulating the semiconductor dies 10 W, according to some exemplary embodiments of the inventive concept.

Referring to FIG. 11A , a sidewall 72 surrounding the semiconductor dies 10 W and a piston 74 movable up and down along the sidewall 72 above the semiconductor dies 10 W may be provided. In this exemplary embodiment, the protective film 40 may be provided at the tops of the semiconductor dies 10 W.

The sidewall 72 may be in close contact with a top surface of the protective film 40 . For example, the entire bottom surface of the sidewall 72 may be in contact with the top surface of the protective film 40 . A pressure in an inner space defined by the sidewall 72 , the piston 74 , and the protective film 40 may be substantially the same as a pressure outside the sidewall 72 . In this exemplary embodiment, the piston 74 may have a height H 1 .

Referring to FIG. 11B , the height of the piston 74 may be reduced to a height H 2 to increase the pressure in the inner space. Since the inner space is substantially sealed, the pressure in the inner space may be increased as the height of the piston 74 is reduced to the height H 2 . For example, as the height of the piston 74 is reduced, the pressure in the inner space is increased.

When the pressure in the inner space is increased, the increased pressure may be transmitted to the semiconductor dies 10 W through the protective film 40 , so that the warpage of the semiconductor dies 10 W and the adhesive film 20 B may be reduced or alleviated by the transmitted pressure.

When the protective film 40 does not exist, the warpage of the semiconductor dies 10 W and the adhesive film 20 B is not reduced or alleviated even if the pressure in the inner space is increased. This is because the increased pressure in the inner space is applied to not only the top surfaces of the semiconductor dies 10 W but also bottom surfaces of portions of the adhesive film 20 B detached from the base film 30 A.

Accordingly, the protective film 40 may be needed when the sidewall 72 and the piston 74 are used, as shown in FIGS. 11A and 11B .

Subsequent processes are the same as those described with reference to FIGS. 8 and 9 . Thus, redundant descriptions will be omitted.

When using a method of singulating semiconductor dies and a method of fabricating a semiconductor package, according to example embodiments of the inventive concept, device reliability may be increased and a failure rate may be decreased.

FIG. 12 is a diagram of a semiconductor package 200 fabricated according to an exemplary embodiment of the inventive concept.

Referring to FIG. 12 , a semiconductor die 220 may be mounted on a package substrate 210 . The semiconductor die 220 may be the semiconductor die 10 F picked up by the collet 62 in FIG. 9 . The semiconductor die 220 may be flash memory, phase-change random access memory (PRAM), resistive RAM (PRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), a logic device, or a controller but is not limited thereto. The flash memory may be NAND flash memory.

A plurality of first terminals 212 may be formed in the package substrate 210 . The package substrate 210 may be a printed circuit board (PCB) or a flexible PCB (FPCB).

The first terminals 212 may be bump pads of which each may have a bump bonded thereto. The first terminals 212 may have a structure of a single metal layer or a structure in which a plurality of metals are stacked. The first terminals 212 may include copper (Cu), aluminum (Al), nickel (Ni), or an alloy of at least two elements thereof, but the inventive concept is not limited thereto.

The semiconductor die 220 may include a plurality of second terminals 222 respectively corresponding to the first terminals 212 . Each of the second terminals 222 may be connected to a corresponding one of the first terminals 212 by a solder bump 230 .

The various pads of a device described herein may be conductive terminals connected to internal wiring and/or logic circuits of the device, and may transmit signals and/or supply voltages between an internal wiring and/or internal circuit of the device and an external source. For example, bump pads of the semiconductor die 220 may electrically connect to and transmit supply voltages and/or signals between an integrated circuit of the semiconductor die 220 and a device to which the semiconductor die 220 is connected. The various pads may be provided on or near an external surface of the device and may generally have a planar surface area (often larger than a corresponding surface area of the internal wiring to which they are connected) to promote connection to a further terminal, such as a bump or solder ball, and/or an external wiring.

To verify the effect of a method of irradiating UV rays after alleviating warpage by applying a pressure as described above, fixation areas were measured and compared with respect to cases of not using gas spraying, of spraying gas for 30 seconds, and of spraying gas for 100 seconds, and the comparison result is shown in FIG. 13 .

Air was sprayed as the gas. The case of spraying gas for 30 seconds was different from the case of spraying gas for 100 seconds in terms of only spraying time. A fixation area was measured using a trace of fixation remaining in a base film.

Referring to FIG. 13 , fixation areas are expressed as percentages with respect to the area of a semiconductor die with respect to the cases of not using air spraying, of spraying the air for 30 seconds, and of spraying the air for 100 seconds.

As a result, while the percentage of a fixation area was about 1% in the case of not using air spraying, the percentage of a fixation area was about 0.7% in the case of spraying the air for 30 seconds. In addition, the percentage of a fixation area was decreased to about 0.2% in the case of spraying the air for 100 seconds.

Therefore, it has been verified that when warpage of a semiconductor die is removed by applying a pressure to the semiconductor die, a fixation area may be decreased, and furthermore, a failure rate may be decreased and device reliability may be increased.

While the inventive concept has been particularly shown and described with reference to example embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.